Microwave just stopped working. Here is what I've checked so far:
- power to unit good
- front panel display works
- fuse is good
- timer, clock, fan and under unit light work
- inside light does not work
When trying to heat a cup of water get the following display message: open and close door, press start. Each time I try this I get the same message.

Tested both door switches and they show the proper continuity. Looked at the door interlock cams and didn't see where the micro switch is engaged when the door is closed. Switch button only is engaged while passing the middle of the cam. Took the door interlocks out (both top and bottom) and saw that the top door interlock actually has 2 micro switches. Checked the 3rd switch and see good continuity. Someone suggested to replace both interlock support cams and springs. This doesn't seem like a fix to me. If it is the problem it would indicate that all 3 interlock cams wore down at the same rate and time.
Debating whether to spend 1/2 the price of a new microwave or not.

A faulty door switch can also restrict the functioning of your micriwave so please once check this also and if there it is faulty one then replace it.
To test whether the door switch is working fine or not
you can do it by following the below provided information:

A door switch is a simple on/off mechanism that prohibits the microwave from operating when the door is open. Microwave door switches are only an inch long. Most are black in color and all have metal prongs, called terminals, extending out from the body of the switch. Microwave door switches are normally mounted to a bracket near the door latch. Also, microwaves usually have three or four door switches.

There is a latch (sometimes referred to as a hook) attached to the inside of your microwave door that comes in contact with and activates the door switch when the door is closed. Examine this prong first. You may not be experiencing any problems with your door switch. Perhaps the latch on the inside of your microwave door is missing or damaged, leaving it unable to activate the door switch.

Some door switches have only two metal prongs extending from the body, while others have three. Those with three terminals will have a common (COM) terminal, a normally closed (N.C.) terminal, and a normally open (N.O.) terminal. Those switches with only two terminals will have either a common terminal and a normally open terminal, or a common terminal and a normally closed terminal. We are providing directions for testing a door switch with three terminals. If you are dealing with a door switch that has only two terminals, ignore the part of this test that does not apply to you.

Using caution, remove all wiring harness leads from the switch's terminals. Be aware that some door switches may have a locking clip keeping the harness from coming loose. In this case, there is a protruding lever which must be depressed while the harness is gently pulled away from the terminal.

Use your ohmmeter to test your switch for continuity. Begin by setting your ohmmeter to measure resistance at a scale of Rx1. If you are using an analog meter, touch the metal tips of the test leads together and zero your ohmmeter by adjusting the thumbwheel in the front of the meter until the needle reads '0' on the scale.

Touch one meter lead to the COM terminal and the other lead to the N.O. terminal. Do not push in on the actuator. Your meter should give a reading of infinity, meaning the circuit is open, and there is no continuity. Without moving the meter's leads, press down on the actuator until you hear a 'click'. With the 'click' of the actuator, the meter should produce a resistance reading of zero ohms. This means the circuit is closed and continuity is present.